Power convertor and controlling method thereof

Abstract

A power converter includes a conversion circuit, an auxiliary circuit, and a controller. The conversion circuit includes a changeover switch that adjusts an output voltage based on a first control signal and a magnetic element. The magnetic element includes a primary winding configured to receive an input voltage and a secondary winding configured to provide an output voltage. The primary winding is coupled to the changeover switch. The auxiliary circuit includes an auxiliary winding configured to provide an auxiliary voltage, an energy storage unit configured to store the auxiliary voltage, and a voltage regulation unit to receive the auxiliary voltage and provide an operating voltage. The auxiliary winding is magnetically coupled to the magnetic element, and the voltage regulation unit is coupled to the auxiliary winding and the energy storage unit in parallel. The controller receives the operating voltage from the voltage regulation unit.

Description

[Technical Field]

[0001] This case relates to a power converter, and more particularly to a power converter with controllable switching duty cycle. [Previous Technology]

[0002] The voltage supplied to a pulse width modulation (PWM) controller typically comes from the voltage mapped from the secondary winding to the auxiliary winding. When the specified output voltage range expands to 48 volts (V), the voltage mapped back to the controller will also vary widely with the output voltage. At a minimum output voltage of 5V, it must be considered that this voltage is sufficient for the controller. If the controller requires 15V (i.e., the ratio of turns in the secondary winding to the auxiliary winding is 1:3), then the voltage range mapped back to the auxiliary winding from the output voltage range of 5V to 48V will be 15V to 144V, which is far higher than the IC's internal withstand voltage. If this voltage is stepped down to 15V and supplied to the controller via a low dropout regulator (LDO), a voltage of 129V will be across the LDO. At an output voltage of 48V, this will result in significant power consumption, failing to meet increasingly stringent energy efficiency regulations. Therefore, how to provide power conversion to solve the above problems is an important issue in this field. [Summary of the Invention]

[0003] A power converter includes a conversion circuit, an auxiliary circuit, and a controller. The conversion circuit includes a switching switch and a magnetic element for adjusting the output voltage according to a first control signal. The magnetic element includes a primary winding for receiving an input voltage and a secondary winding for providing an output voltage. The primary winding is coupled to the switching switch. The auxiliary circuit includes an auxiliary winding for providing an auxiliary voltage, an energy storage unit for storing the auxiliary voltage, and a voltage regulating unit for receiving the auxiliary voltage and providing an operating voltage. The auxiliary winding is magnetically coupled to the magnetic element, and the voltage regulating unit is connected in parallel with the auxiliary winding and the energy storage unit. The controller receives the operating voltage from the voltage regulating unit.

[0004] A control method for a power converter, wherein the power converter includes a switching circuit having a switching switch and a magnetic element, an auxiliary circuit having an auxiliary winding, an energy storage unit, and a voltage regulation unit having the auxiliary winding and the energy storage unit connected in parallel, and a controller. The magnetic element includes a primary winding and a secondary winding, wherein the control method includes: receiving an input voltage through the primary winding; adjusting the output voltage through the switching switch according to a first control signal; providing the output voltage through the secondary winding; providing an auxiliary voltage to the energy storage unit through the auxiliary winding according to one of the input voltage and the output voltage; providing an operating voltage to the controller through the voltage regulation unit according to the auxiliary voltage; and obtaining a comparison result between the operating voltage and the rated voltage through the controller to adjust the duty cycle of the regulating switch in the voltage regulation unit.

Implementation Method

[0005] The following detailed description is based on embodiments and accompanying drawings. However, the embodiments provided are not intended to limit the scope of this disclosure, and the description of the structural operation is not intended to limit the order of execution. Any structure resulting from the recombination of elements and producing a device with equivalent functionality is within the scope of this disclosure. Furthermore, the illustrations are for illustrative purposes only and are not drawn to their original dimensions. For ease of understanding, the same or similar elements will be labeled with the same symbols in the following description.

[0006] As used herein, “coupled”, “connected” or “linked” may refer to two or more components making direct physical or electrical contact with each other, or making indirect physical or electrical contact with each other, or to two or more components operating or acting on each other.

[0007] In this document, the term "circuit" refers to an object consisting of one or more transistors and / or one or more active and passive components connected in a certain manner to process signals.

[0008] In this document, the magnitude of the values ​​is not intended to limit this disclosure. Any person skilled in the art may make various modifications and embellishments without departing from the spirit and scope of this disclosure.

[0009] Unless otherwise specified, the terms used throughout this specification and the claims generally have their ordinary meaning in the context of the art, the disclosure, and the specific content. Furthermore, the terms "comprising," "including," "having," "containing," etc., used herein are open-ended terms, meaning "including but not limited to." Additionally, the term "and / or" as used herein includes any one or more of the related listed items and all combinations thereof.

[0010] Please refer to Figure 1, which is a schematic diagram of a power converter 100 according to an embodiment of the present disclosure. As shown in Figure 1, the power converter 100 includes a bridge rectifier 110, a conversion circuit 120, an auxiliary circuit 130, and a controller U1. In some embodiments, the controller U1 is used to generate signals to control the operation of the conversion circuit 120 and the auxiliary circuit 130, and may be a microprocessor or any suitable integrated circuit.

[0011] In some embodiments, the bridge rectifier 110 is used to convert the alternating current (AC) entering the power converter 100 into direct current (DC). The bridge rectifier 110 is coupled between the positive and negative terminals of the input capacitor CI.

[0012] In some embodiments, the switching circuit 120 includes a magnetic element 121, a switching switch Q1, an input capacitor CI, an output capacitor CO, and a diode DO. The magnetic element 121 includes a primary winding N1 and a secondary winding N2. The switching switch Q1 switches on or off in response to a signal Vgs_Q1 received at its gate terminal. The source and drain terminals of the switching switch Q1 have a signal Vds_Q1 opposite to the signal Vgs_Q1 in response to the signal Vgs_Q1. The input capacitor CI is coupled between the non-point terminal and the ground terminal of the primary winding N1. The switching switch Q1 is coupled between the point terminal and the ground terminal of the primary winding N1. The point terminal of the secondary winding N2 is coupled to the positive terminal of the diode DO, and the non-point terminal of the secondary winding N2 is coupled to the ground terminal. The output capacitor CO is coupled between the negative terminal of the diode DO and the ground terminal.

[0013] In some embodiments, the auxiliary circuit 130 includes an energy storage unit 131, a voltage regulation unit 132, an auxiliary winding N3, and an energy storage capacitor C2. The energy storage unit 131 includes an auxiliary capacitor C1 and an auxiliary diode D1. The voltage regulation unit 132 includes an adjustment switch Q2, an adjustment diode D2, and an adjustment inductor L1. The adjustment switch Q2 switches on or off in response to a signal Vgs_Q2 received at its gate terminal. The point terminal of the auxiliary winding N3 is coupled to the positive terminal of the auxiliary diode D1, the negative terminal of the auxiliary diode D1 is coupled to node n2, and the non-point terminal of the auxiliary winding N3 is coupled to node n1. The auxiliary capacitor C1 is coupled between node n1 and node n2. The adjustment switch Q2 is coupled between node n2 and ground. The positive terminal of the adjustment diode D2 is coupled to node n1, and the negative terminal of the adjustment diode D2 is coupled to node n3. The regulating inductor L1 is coupled between node n1 and the ground terminal. The energy storage capacitor C2 is coupled between node n3 and the ground terminal.

[0014] In some embodiments, the withstand voltage of the switching switch Q1 is greater than the withstand voltage of the regulating switch Q2.

[0015] In some embodiments, the auxiliary winding N3 is in the same direction as the primary winding N1 (i.e., the starting point (end) of the winding is the same), and the auxiliary winding N3 is in the opposite direction to the secondary winding N2 (i.e., the starting point (end) of the winding is opposite).

[0016] In some embodiments, the auxiliary diode D1, the regulating diode D2, and the diode DO may be replaced with metal oxide semiconductor field effect transistors (MOSFETs).

[0017] In some embodiments, the controller U1 includes an output signal terminal GATE1, an output signal terminal GATE2, a receiving voltage terminal VCC, and a ground terminal GND. The controller U1 outputs a signal Vgs_Q1 at the output signal terminal GATE1 to the gate terminal of the switching switch Q1. The controller U1 outputs a signal Vgs_Q2 at the output signal terminal GATE2 to the gate terminal of the regulating switch Q2. The controller U1 receives voltage from the voltage regulating unit 132. The controller U1 is coupled to the ground terminal GND.

[0018] Please refer to Figures 2, 3, and 4 to 5 together. Figure 2 is a flowchart illustrating the control method 200 of the power converter 100 in Figure 1 according to an embodiment of the present invention. Figure 3 is a control timing diagram 300 of the power converter 100 according to an embodiment of the present invention. Figures 4 and 5 are schematic diagrams illustrating the operation of the power converter 100 in Figure 1 during various periods according to an embodiment of the present invention. In some embodiments, the controller U1 executes the control method 200 of the power converter 100 to control the operation of the power converter 100.

[0019] In some embodiments, signals Vgs_Q1 and Vgs_Q2 are different signals and have no sequential relationship in operation. Therefore, the control timing diagram 300 is only one embodiment of this case and does not mean that signals Vgs_Q1 and Vgs_Q2 must be the same signal or must have a sequential relationship in operation.

[0020] In some embodiments, the time points t1 to t4 and ta to td represent different times from each other. Specifically, the operating frequencies of signals Vgs_Q1 and Vd_D1 are much lower than the operating frequency of signal Vgs_Q2.

[0021] According to step S210, the input capacitor CI is charged to the input voltage VI in response to the conversion voltage output by the bridge rectifier 110. The primary winding N1 receives the input voltage VI from the input capacitor CI.

[0022] According to step S220, during the period from time point t1 to t2 shown in Figure 3, the switching switch Q1 is turned on in response to the high-potential signal Vgs_Q1. At this time, the non-point terminals of the primary winding N1 and the secondary winding N2 are at high potentials. Because the point terminal of the secondary winding N2 is at a low potential, the diode DO of the output capacitor CO is in an open state, and the secondary winding N2 cannot charge the output capacitor CO.

[0023] In some embodiments, the diode DO is in a switch-off state in response to its positive terminal being at a low potential and its negative terminal being at a high potential. Specifically, the non-point terminals of the primary winding N1 and the secondary winding N2 are at high potentials, so the positive terminal of the diode DO coupled to the point terminal of the secondary winding N2 is at a low potential, while the negative terminal of the diode DO is relatively at a high potential, causing the diode DO to be switched off.

[0024] In some embodiments, the auxiliary diode D1 is in an off state in response to its positive terminal being at a low potential and its negative terminal being at a high potential. Specifically, the non-point terminal of the auxiliary winding N3 responds to the non-point terminal of the secondary winding N2 being at a high potential. Therefore, the positive terminal of the auxiliary diode D1 coupled to the point terminal of the auxiliary winding N3 is at a low potential, while the negative terminal of the auxiliary diode D1 is relatively at a high potential, causing the auxiliary diode D1 to be off. At this time, the auxiliary diode D1 has a high potential signal Vd_D1 due to the reverse bias voltage generated by the off state.

[0025] According to step S230, during the period from time point t2 to t3, as shown in Figure 3, the switching switch Q1 is disconnected in response to the low-potential signal Vgs_Q1. At this time, the terminals of the primary winding N1 and the secondary winding N2 are at high potentials in response to the signal Vgs_Q1. Because the terminals of the secondary winding N2 are at high potentials, the diode DO of the output capacitor CO is in a conducting state, and the secondary winding N2 can charge the output capacitor CO.

[0026] In some embodiments, the diode DO is in a conducting state in response to its positive terminal being at a high potential and its negative terminal being at a low potential. Specifically, the terminals of the primary winding N1 and the secondary winding N2 are at high potentials, so the positive terminal of the diode DO coupled to the terminal of the secondary winding N2 is at a high potential, while the negative terminal of the diode DO is at a relatively low potential, causing the diode DO to conduct.

[0027] In some embodiments, the auxiliary diode D1 is in a conducting state in response to its positive terminal being at a high potential and its negative terminal being at a low potential. Specifically, the terminal of the auxiliary winding N3 is at a high potential in response to the terminal of the secondary winding N2, so the positive terminal of the auxiliary diode D1 coupled to the terminal of the auxiliary winding N3 is at a high potential, while the negative terminal of the auxiliary diode D1 is relatively at a low potential, thus turning the auxiliary diode D1 on.

[0028] According to step S240, during the period from time point t2 to t3, as shown in Figure 3, the auxiliary winding N3 provides an auxiliary voltage VC1 to the energy storage unit 131 based on either the input voltage VI or the output voltage VO.

[0029] In some embodiments, when the ratio of the maximum rated output voltage value of the output voltage VO to the minimum rated output voltage value is less than the ratio of the maximum rated input voltage value of the input voltage VI to the minimum rated input voltage value, the auxiliary winding N3 provides an auxiliary voltage VC1 to the energy storage unit 131 according to the output voltage VO. Specifically, when the output voltage VO varies from 5V to 10V (with a ratio of 2) and the input voltage VI varies from 100V to 240V (with a ratio of 2.4), the auxiliary winding N3 provides an auxiliary voltage VC1 to the auxiliary capacitor C1 according to the output voltage VO.

[0030] In some embodiments, the auxiliary voltage VC1 is based on the formula (1): VC1 = VO x N3 / N2…(1) VC1 represents the auxiliary voltage VC1, VO represents the output voltage VO, N3 represents the number of turns of the auxiliary winding N3, and N2 represents the number of turns of the secondary winding N2.

[0031] According to step S250, in some embodiments, during the period from time point tb to tc, as shown in Figures 3 and 4, the regulating switch Q2 is turned on in response to a signal Vgs_Q2 having a high potential. The auxiliary capacitor C1 charges the regulating inductor L1 through the current IQ2 flowing through the regulating switch Q2 and the regulating inductor L1 (in some embodiments, the current IL1 and the current IQ2 are the same current in certain timing sequences).

[0032] According to step S250, during the period from time point tc to td, as shown in Figures 3 and 5, the regulating switch Q2 is disconnected in response to a low-potential signal Vgs_Q2. The regulating inductor L1 charges the energy storage capacitor C2 through the current ID2 flowing through the regulating diode D2, so that the energy storage capacitor C2 has an operating voltage VC2. The controller U1 receives the operating voltage VC2 at the receiving voltage terminal VCC. (In some embodiments, the current IL1 and the current ID2 in certain timings are the same current).

[0033] According to step S260, the comparison result of the operating voltage VC2 and the rated voltage (the voltage required to drive the controller U1) is obtained through the controller U1, so as to adjust the duty cycle of the regulating switch Q2 in the voltage regulating unit 132.

[0034] In one embodiment, the power converter 100 has a detection circuit (not shown) to detect the operating voltage VC2.

[0035] In some embodiments, the power converter 100 has a comparator circuit (not shown) to determine, according to step S270, whether the operating voltage VC2 is greater than the rated voltage. If yes, proceed to step S280; if no, proceed to step S290.

[0036] In step S280, the duty cycle of the regulating switch Q2 is controlled to be less than a certain ratio by the output signal Vgs_Q2 of the controller U1.

[0037] For example, when the operating voltage VC2 is 10V and the rated voltage is 5V, the controller U1 responds to the comparison result that the operating voltage VC2 is greater than the rated voltage, and the controller U1 outputs the signal Vgs_Q2 to control the duty cycle of the regulating switch Q2 to be less than a certain ratio.

[0038] In step S290, the duty cycle of the regulating switch Q2 is controlled to be greater than a certain ratio by the output signal Vgs_Q2 of the controller U1.

[0039] For example, if the operating voltage VC2 is 3V and the rated voltage is 5V, then the controller U1 will respond to the comparison result that the operating voltage VC2 is less than the rated voltage, and the controller U1 will output signal Vgs_Q2 to control the duty cycle of the regulating switch Q2 to be greater than a certain ratio.

[0040] In some embodiments, the ratios mentioned in steps S280 and S290 are variable values ​​because the duty cycle changes with the output voltage VO.

[0041] Please refer to Figures 2, 6, and 7 to 8 together. Figure 6 is a control timing diagram 600 of a power converter 100 according to an embodiment of the present invention. Figures 7 and 8 are schematic diagrams illustrating the operation of the power converter 100 of Figure 1 according to an embodiment of the present invention during various periods. Unless it is necessary to explain the cooperation relationship of components, for the sake of brevity, the specific operation of similar components and steps that have been discussed in detail in the above paragraphs is omitted here.

[0042] Please refer to Figures 7 and 8. Compared with the power converter 100 in Figures 1, 4 and 5, the point end of the auxiliary winding N3 is coupled to node n1, and the non-point end of the auxiliary winding N3 is coupled to the positive end of the auxiliary diode D1.

[0043] As shown in Figure 7, the auxiliary winding N3 is in the opposite direction to the primary winding N1 (i.e., the starting points (ends) of the windings are opposite), and the auxiliary winding N3 is in the same direction as the secondary winding N2 (i.e., the starting points (ends) of the windings are the same).

[0044] In some embodiments, steps S230 and S240 may be interchanged.

[0045] According to step S210, the input capacitor CI is charged to the input voltage VI in response to the conversion voltage output by the bridge rectifier 110. The primary winding N1 receives the input voltage VI from the input capacitor CI.

[0046] According to step S220, during the period from time point t1 to t2, as shown in Figure 6, the switching switch Q1 is turned on in response to the high-potential signal Vgs_Q1. At this time, the non-point terminals of the primary winding N1 and the secondary winding N2 are at high potentials in response to the signal Vgs_Q1. Because the point terminal of the secondary winding N2 is at a low potential, the diode DO of the output capacitor CO is in the open state, and the secondary winding N2 cannot charge the output capacitor CO.

[0047] In some embodiments, the auxiliary diode D1 is in a conducting state in response to its positive terminal being at a high potential and its negative terminal being at a low potential. Specifically, the non-point terminal of the auxiliary winding N3 is at a high potential in response to the non-point terminal of the primary winding N1. Therefore, the positive terminal of the auxiliary diode D1 coupled to the non-point terminal of the auxiliary winding N3 is at a high potential, while the negative terminal of the auxiliary diode D1 is relatively at a low potential, thus turning the auxiliary diode D1 on.

[0048] Following step S220, according to step S240, during the period from time point t1 to t2, as shown in Figure 6, the auxiliary winding N3 provides an auxiliary voltage VC1 to the energy storage unit 131 based on either the input voltage VI or the output voltage VO.

[0049] In some embodiments, when the ratio of the maximum rated output voltage value of the output voltage VO to the minimum rated output voltage value is greater than the ratio of the maximum rated input voltage value of the input voltage VI to the minimum rated input voltage value, the auxiliary winding N3 provides an auxiliary voltage VC1 to the energy storage unit 131 according to the input voltage VI. Specifically, when the output voltage VO varies from 5V to 15V (with a ratio of 3 times) and the input voltage VI varies from 100V to 240V (with a ratio of 2.4 times), the auxiliary winding N3 provides an auxiliary voltage VC1 to the auxiliary capacitor C1 according to the input voltage VI.

[0050] In some embodiments, the auxiliary voltage VC1 is based on the formula (2): VC1 = VI x N3 / N1…(2) VC1 represents the auxiliary voltage VC1, VI represents the input voltage VI, N3 represents the number of turns of the auxiliary winding N3, and N1 represents the number of turns of the primary winding N1.

[0051] Continuing from step S240, according to step S230, during the period from time point t2 to t3, as shown in Figure 6, the switching switch Q1 is disconnected in response to the low-potential signal Vgs_Q1. At this time, the terminals of the primary winding N1 and the secondary winding N2 are at high potentials in response to the signal Vgs_Q1. Because the terminals of the secondary winding N2 are at high potentials, the output capacitor CO can be charged by the secondary winding N2.

[0052] In some embodiments, the auxiliary diode D1 is in an open state in response to its positive terminal being at a low potential and its negative terminal being at a high potential. Specifically, the point terminal of the auxiliary winding N3 responds to the point terminal of the primary winding N1 being at a high potential. Therefore, the positive terminal of the auxiliary diode D1, which is coupled to the non-point terminal of the auxiliary winding N3, is at a low potential, while the negative terminal of the auxiliary diode D1 is relatively at a high potential, causing the auxiliary diode D1 to be open. At this time, the auxiliary diode D1 has a high potential signal Vd_D1, which is the reverse bias voltage generated due to the open state.

[0053] Following step S230, according to step S250, in some embodiments, as shown in Figures 6 and 7, during the period from time point tb to tc, the regulating switch Q2 is turned on in response to a signal Vgs_Q2 having a high potential. The auxiliary capacitor C1 charges the regulating inductor L1 through the current IQ2 flowing through the regulating switch Q2 and the regulating inductor L1 (in some embodiments, the current IL1 and the current IQ2 are the same current in certain timing sequences).

[0054] According to step S250, during the period from time point tc to td, as shown in Figures 6 and 8, the regulating switch Q2 is disconnected in response to a signal Vgs_Q2 with a low potential. The regulating inductor L1 charges the energy storage capacitor C2 through the current ID2 flowing through the regulating diode D2 (in some embodiments, the current IL1 and the current ID2 are the same current in certain timings), so that the energy storage capacitor C2 has an operating voltage VC2. The controller U1 receives the operating voltage VC2 at the receiving voltage terminal VCC.

[0055] According to step S260, the comparison result between the operating voltage VC2 and the rated voltage is obtained through the controller U1, so as to adjust the duty cycle of the regulating switch Q2 in the voltage regulating unit 132.

[0056] According to step S270, determine whether the operating voltage is greater than the rated voltage. If yes, proceed to step S280; if no, proceed to step S290.

[0057] In step S280, the duty cycle of the regulating switch Q2 is controlled to be less than a certain ratio by the output signal Vgs_Q2 of the controller U1.

[0058] In step S290, the duty cycle of the regulating switch Q2 is controlled to be greater than a certain ratio by the output signal Vgs_Q2 of the controller U1.

[0059] In some embodiments, the ratios mentioned in steps S280 and S290 are variable values ​​because the duty cycle changes with the input voltage VI.

[0060] In some embodiments, the duty cycle is based on the formula (3): D = VCC / (VCC + VC1)…(3) D represents the duty cycle, VCC represents the rated voltage, and VC1 represents the auxiliary voltage VC1.

[0061] Please refer to Figure 9, which is a schematic diagram of a power converter 900 according to an embodiment of the present disclosure. Compared to the power converter 100 in Figure 1, the regulating switch Q2 can be coupled inside the controller U1. In other words, the regulating switch Q2 can be integrated within the controller U1.

[0062] In summary, the power converter and its control method disclosed herein control the duty cycle of the regulating switch based on the difference between the output voltage and the rated voltage of the drive controller, so as to regulate the voltage supplied from the auxiliary winding to the controller, avoid generating excessive power consumption, and meet increasingly stringent energy efficiency regulations.

[0063] Although the present disclosure has been disclosed above with reference to embodiments, it is not intended to limit the present disclosure. Any person with ordinary knowledge in the art may make various modifications and alterations without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the claims attached. [Simplified Explanation of the Diagram]

[0064] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the accompanying drawings are described below: Figure 1 is a schematic diagram of a power converter according to an embodiment of this disclosure. Figure 2 is a flowchart illustrating the control method of the power converter of Figure 1 according to an embodiment of this invention. Figure 3 is a control timing diagram of the power converter according to an embodiment of this invention. Figures 4 and 5 are schematic diagrams illustrating the operation of the power converter of Figure 1 according to an embodiment of this invention during various periods. Figure 6 is a control timing diagram of the power converter according to an embodiment of this invention. Figures 7 and 8 are schematic diagrams illustrating the operation of the power converter of Figure 1 according to an embodiment of this invention during various periods. Figure 9 is a schematic diagram of a power converter according to an embodiment of this disclosure.

Claims

1. A power converter, comprising: a conversion circuit including: a switching switch for adjusting an output voltage according to a first control signal; and a magnetic element including: a primary winding coupled to the switching switch and receiving an input voltage; and a secondary winding for providing the output voltage; an auxiliary circuit including: an auxiliary winding magnetically coupled to the magnetic element and providing an auxiliary voltage; an energy storage unit for storing the auxiliary voltage; and a voltage regulation unit connected in parallel with the auxiliary winding and the energy storage unit, receiving the auxiliary voltage and providing an operating voltage, wherein the voltage regulation unit includes: a regulating inductor including a first terminal coupled to the auxiliary winding and a second terminal coupled to a ground terminal; and a controller receiving the operating voltage from the voltage regulation unit.

2. The power converter as claimed in claim 1, wherein the auxiliary winding is in the same direction as the primary winding and the auxiliary winding is in the opposite direction to the secondary winding.

3. The power converter as claimed in claim 2, wherein the energy storage unit comprises: an auxiliary capacitor coupled to a non-point terminal of the auxiliary winding; and an auxiliary diode coupled between a point terminal of the auxiliary winding and the auxiliary capacitor.

4. The power converter as claimed in claim 3, wherein the voltage regulation unit further comprises: a regulating switch, a first terminal of which is coupled between the auxiliary capacitor and the auxiliary diode, a second terminal of which is coupled between the regulating inductor and a ground terminal, and a third terminal of which is coupled to the controller; and a regulating diode, a first terminal of which is coupled between the regulating inductor, the auxiliary capacitor and the auxiliary winding, and a second terminal of which is coupled to an input terminal of the controller that receives the operating voltage.

5. The power converter as claimed in claim 4, wherein the auxiliary circuit further includes an energy storage capacitor coupled between the input terminal and the regulating diode.

6. The power converter as described in claim 4, wherein: When the operating voltage is greater than a rated voltage, the controller controls the duty cycle of the regulating switch to be less than a certain percentage according to a second control signal; and when the operating voltage is less than the rated voltage, the controller controls the duty cycle to be greater than the percentage according to the second control signal, wherein the first control signal and the second control signal are different from each other.

7. The power converter as claimed in claim 1, wherein the auxiliary winding is in the opposite direction to the primary winding and the auxiliary winding is in the same direction as the secondary winding.

8. The power converter as claimed in claim 7, wherein the energy storage unit comprises: an auxiliary capacitor coupled to a point terminal of the auxiliary winding; and an auxiliary diode coupled between a non-point terminal of the auxiliary winding and the auxiliary capacitor.

9. The power converter as described in claim 8, wherein: When the switch is turned on, the auxiliary diode is turned on and the auxiliary winding charges the auxiliary capacitor; when the switch is turned off, the auxiliary diode is turned off and the auxiliary winding does not charge the auxiliary capacitor.

10. The power converter as claimed in claim 8, wherein the voltage regulation unit further comprises: a regulating switch, a first terminal of which is coupled between the auxiliary capacitor and the auxiliary diode, a second terminal of which is coupled between the regulating inductor and a ground terminal, and a third terminal of which is coupled to the controller; and a regulating diode, a first terminal of which is coupled between the regulating inductor, the auxiliary capacitor, and the auxiliary winding, and a second terminal of which is coupled to an input terminal of the controller that receives the operating voltage.

11. The power converter as claimed in claim 10, wherein the auxiliary circuit further includes an energy storage capacitor coupled between the controller and the regulating diode.

12. The power converter as described in claim 10, wherein: When the operating voltage is greater than a rated voltage, the controller controls the duty cycle of the regulating switch to be less than a certain percentage according to a second control signal; and when the operating voltage is less than the rated voltage, the controller controls the duty cycle to be greater than the percentage according to the second control signal, wherein the first control signal and the second control signal are different from each other.

13. The power converter as claimed in claim 8, wherein the voltage regulation unit further comprises: a regulating diode, a first terminal of the regulating diode being coupled to the regulating inductor, and a second terminal of the regulating diode being coupled to an input terminal of the controller for receiving the operating voltage; wherein the controller comprises: a regulating switch, the controller controlling a duty cycle of the regulating switch according to a rated voltage and a second control signal controlling the regulating switch.

14. The power converter as claimed in claim 13, wherein a withstand voltage value of the switching switch is greater than a withstand voltage value of the regulating switch.

15. A control method for a power converter, wherein the power converter includes a switching circuit having a switching switch and a magnetic element, an auxiliary circuit having an auxiliary winding, an energy storage unit, and a voltage regulation unit connected in parallel with the auxiliary winding and the energy storage unit, and a controller, wherein the magnetic element includes a primary winding and a secondary winding, wherein the control method includes: receiving an input voltage through the primary winding; adjusting an output voltage through the switching switch according to a first control signal; providing the output voltage through the secondary winding; providing an auxiliary voltage to the energy storage unit through the auxiliary winding according to one of the input voltage and the output voltage; providing an operating voltage to the controller through the voltage regulation unit according to the auxiliary voltage; and obtaining a comparison result between the operating voltage and a rated voltage through the controller to adjust a duty cycle of a regulating switch in the voltage regulation unit.

16. The control method as described in claim 15 further comprises: when the comparison result indicates that the operating voltage is greater than the rated voltage, controlling the duty cycle of the regulating switch to be less than a ratio via the controller according to a second control signal.

17. The control method as described in claim 15 further comprises: when the comparison result indicates that the operating voltage is less than the rated voltage, controlling the duty cycle of the regulating switch to be greater than a ratio via the controller according to a second control signal.

18. The control method as described in claim 15 further comprises: when the auxiliary winding is in the same direction as the primary winding and the auxiliary winding is in the opposite direction to the secondary winding, providing the auxiliary voltage to the energy storage unit through the auxiliary winding according to the output voltage.

19. The control method as described in claim 18 further comprises: charging an auxiliary capacitor contained in the auxiliary circuit through the auxiliary winding when the switching switch is off.

20. The control method as described in claim 15 further comprises: when the auxiliary winding is in the opposite direction to the primary winding and in the same direction as the secondary winding, providing the auxiliary voltage to the energy storage unit through the auxiliary winding according to the input voltage; and when the switching switch is turned on, charging an auxiliary capacitor included in the auxiliary circuit through the auxiliary winding.

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